/Engine/Plugins/Experimental/GeometryScripting/Source/GeometryScriptingCore/Public/GeometryScript/MeshQueryFunctions.h
Static UPARAM(DisplayName = "Triangle Count") int32 GetTriangleCount( UDynamicMesh* TargetMesh ); Gets the number of Triangle IDs in the mesh. This may be larger than the Triangle Count if the mesh is not dense, even after deleting triangles.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintPure, Category="GeometryScript|MeshQueries", Meta=(ScriptMethod)) static int32 GetNumTriangleIDs ( [UDynamicMesh](API\Runtime\GeometryFramework\UDynamicMesh) * TargetMesh )